Refining of residual shale oils



United States Patent O tion of California Filed Dec. 31, 1958, Ser. No. 784,308 13 Claims. (Cl. 208-11) This invention relates to the rening of shale oils containing residual fractions, such as crude shale oils or bottoms fractions from distillation of crude shale oils. It relates particularly to -a process for reiining such oils which involves a combination of catalytic hydrogenation and a preliminary solvent treatment. The invention is especially desirable lfor shale oils produced by downtilow eduction, i.e., by eduction processes using a downilow of hot eduction fluid over a static or upwardly moving bed of shale, as in the N-T-U static bed process and the upwardly moving bed process described in the Berg patent, 2,501,153, but it is also applicable to shale oils produced by shale downow and eduction fluid up-ow processes such as the Bureau of Mines gas combustion process.

Shale oil is not generally susceptible to the same rening methods as petroleum oil, at least with any degree of practicality, because of its high content of impurities such as sulfur compounds and especially oxygen and nitrogen compounds. Hydrogenation will serve to remove such impurities, and consequently hydrogenation might be expected to be a most expeditious and economical method for treating shale oil to produce a product which could be rened by conventional processes used for petroleum oils. When a catalytic hydrogenation process was tried out experimentally on shale oils, it worked fine on distillates, but with residual shale oils the hydrogenation unit preheater and/or catalyst bed rapidly became plugged with `fouling substances, which will Ibe referred to `as gunk, and furthermore, lines and equipment became corroded excessively.

Itis therefore an object of this invention to provide a method for treating residual shale oils prior to hydrogenation in such a manner that the hydrogenation unit will not `become plugged with gunk.

v It is also an object to provide for corrosion reduction of shale oils to permissible corrosion levels.

Briefly, the invention involves solvent treating residual shale oils before hydrogenation. A preferred form of the invention involves a combination of water washing and acetone treating residual shale oils prior to the step of preheating the shale oil in the presence of hydrogen preparatory to catalytic hydrogenation. The treatment should be carried out so that a total of about 2 to 6% by weight (based on the entire original crude oil) is rejected by the solvent. Before describing the invention in more detail, the proble-ms of plugging and corrosion will be illustrated and the test methods used will be described.

In the laboratory continuous catalytic hydrogenation unit, also referred to as the hydrogenation pilot plant, which was used to study the hydrogenation of crude shale oil and other oils, the hydrogen and feed are mixed and the mixture is passed downwardly successively through a preheater and a reactor tube of about 1%" outside diameter containing a suitable catalyst such as cobalt molybdate supported on alumina. Runs were carried out at temperatures of 15G-600 F. Ifor the preheater and 80G-900 1F. for the reactor, pressures of about 3000 p.s.i.g., liquid hourly space velocity of about l-2 volumes per volume of catalyst, mass velocities of about 5-200 pounds of feed plu-s hydrogen per hour per square foot of catalyst cross section, and hydrogen/feed ratios of about 3000-6000 s.c.f. per pound. This pilot plant and Fpice the reaction conditions were designed to simulate practical equipment and conditions lfor commercial operations.

It was found that under all the above conditions using certain feeds the preheater and/ or the top of the catalyst -bed tended to become plugged with gunk to such an extent that not more than about one-half barrel of feed per pound of catalyst could be treated before the pressure drop across the preheater and reactor rose from an initial value less than l" of water to values as high as 290 of water. The feeds which caused such gunk to form so rapidly were the residual shale oils of this invention, i.e. crude shale oil and residual fractions therefrom especially where the crude shale oil was derived by downo-w eduction. Residual oils produced by upilow eduction, with static or downowing shale, showed somewhat less gunking tendency than those derived from upow processes, but still plugged the reactor as above. This gunking occurred whether these residual shale oils had previously been allowed to settle, at ambient temperatures or elevated temperatures of l60-l70 F., or even when they had been liltered through lter paper las line as No. 40 Whatman. Photomicrographs taken at l00 magnification showed that the feed contained some particles of solid or semi-solid nature, and that the filtration removed all coarse particles, but there appeared to be some very fine particles which were not removed by ltration. Since these particles were so extremely line, it would not be expected that they would interfere with fluid flow thro-ugh the preheater or through the catalyst bed, and it is believed that the gunking is caused largely by formation of the gunk under the conditions existing in the preheater and catalyst bed. However, it does not seen to be a Afunction of the catalyst nor to any great extent the function of the material of which the preheater is constructed.

A laboratory test method was devised to test the oil for likelihood of precipitation or gunking tendency, and tests were also conducted in a separate preheater built to simulate oney tube of a commercial heat exchanger. All these tests clearly showed the gunking tendency of the residual shale oils and the absence of gunking tendency of distillate oils. The most convenient test was the laboratory bomb test. This was carried out in a heated 300 ml. shaking autoclave equipped with temperature controls and a pressure gauge. About 250 ml. of the oil were charged to the unit and then hydrogen gas was added to bring the pressure to about 2000 p.s.i.g. The unit was then heated to 600 F. while agitating by shaking and the hydrogen pressure was adjusted to 3000 p.s.i.g. The heat was then turned off and the system was allowed to cool, with shaking, to 400 F. The oil was then `discharged through a micrometallic ne lter (10 micron pore size). Tests of the same feedstocks used in the hydrogenation pilot plant showed that if plugging of this filter occurred in the bomb test it would also occur in the hydrogenation unit preheater and reactor bed, and that if free flow occurred without collection of appreciable gunk on the iilter, the oil would probably be Isuitable from a nouplugging standpoint in the hydrogenation plant.

'Corrosion tests were made by the insertion' of coupons of various metals in contact with shale oil liquid or vapor, with and without hydrogen, in pilot plant equipment, or in simulated laboratory tests of pilot plant and commercial equipment. The coupons are installed on racks and insulated from each other by ceramic rings and glass. Cleaning and preparation of coupon samples during the tests followed specications outlined by ASTM, which involved use of ten percent nitric acid, concentrated nitric acid an hydrochloric acid. Tests were carried out on chrome-moly steel and carbon steel as these have frequent extensive use in refinery equipment. Such tests were made by suspending these metallic coupons at various points in distillation, coking, and hydrogenation units such as the pilot plant described above. These coupons were exposed to temperatures in the range of 200 790 F. for periods of time from 132-342 hours. It was found that every type of residual `shale oil tested was excessively corrosive, i.e. had a corrosion rate yfor various meals in excess of about 0.0083 per year, which igure corresponds to an expected life in commercial operation of about ten years.

As previously indicated, the present invention provides a means for avoiding the diiculties of gunking tendencies and corrosivity as described above. The drawings, which aid in a more complete understanding of the invention are:

FIGURE l, showing a form of the process in which the water and `acetone are both used initially together,

FIGURE 2, showing a form of the process of FIGURE 1 wherein a separate water-washing precedes the acetone treatment, and

FIGURE 3, showing a form wherein the water and acetone treatments are also separate, but the acetone treatment precedes the water treatment.

Referring to FIGURE l, it is there shown that the residual shale oil feed may be heated somewhat and subjected to extraction with water and acetone so as to form an aqueous phase and an oil phase. The aqueous phase may be treated in a rst solvent recovery system to recover any acetone extracted by the water, to recirculate this acetone to the extraction stage, as well as part or all of the water, and to leave a water-soluble residue. The oil phase, referred to hereafter as the first oil phase, may be cooled and additional solvent may be added to cause a rejection of solid or semi-solid material and leave a. second oil phase which is sent to a second solvent recovery system from which the solvent is returned to the extraction stage, and part of it may also be returned to the rejection stage. The oil from the solvent recovery stage may be mixed with hydrogen and subjected to hydrogenation as described above.

'In the modification shown in FIGURE 2, the acetone is not used in the extraction stage, but a small amount of an alcohol may be used to minimize foaming and emulsion tendencies. The irst oil phase lfrom the water extraction is treated with acetone in the rejection stage. A small amount of alcohol or aromatic hydrocarbon such as benzol may be also used in the rejection stage. The acetone and alcohol from the lsecond solvent recovery system are then returned to the rejection stage. While only traces of water remain in the rst oil phase, these traces of water appear to aid the sharpness of separation of the solid or semi-solid material in the rejection stage.

-In the modication shown in FIGURE 3 the residual shale oil is rst treated with acetone in the rejection stage to separate Vsolid or semi-solid oil soluble reject, and the remaining oil, or first oil phase, is subjected to water extraction to obtain the water soluble reject. The second oil phase, from the extraction step, after removal of the solvent, is suitable for hydrogenation. As indicated it is preferable not to remove the acetone from the rst oil phase prior to the water extraction, since it reduces the viscosity of the oil, makes the extraction more ecient, and reduces foaming and emulsion tendencies. However, part or all of the acetone may be removed from the iirst oil phase prior to the water extraction. ln this modication of the process ambient temperatures may be used in both the rejection and the extraction stages, although it may be desirable to use slightly elevated temperatures in the rejection stage and somewhat more elevated temperatures in the extraction stage. `If part o-f the acetone is removed prior to the extraction stage, the temperature used there should be higher than if there is no removal of `acetone between stages.

In the extraction stage of FIGURE l, the ratio of acetone/water may be between about 1/1 and 50/1; and the ratio of total solvent/residual shale oil feed may be between about 1/1 and 5/1. Temperature of treatment is preferably about iF. and 180 iF., but it may be as high as 200 F. and as low as 60 F. in some cases. Pressures are elevated if necessary to maintain the liquid phase, `but are generally between 0 `and 200 p.s.i.g. The contacting may be carried out under batch or continuous processing conditions. If additional acetone is added in the rejection step, the amount of acetone in the mixture used for extraction may be reduced, but there should be at least about 10% of acetone in the mixture used for extraction, and the ratio of water/oil should not be lower than about 0.05/1. The material extracted amounts to about 0.05 to 1% of the feed, and consists largely of inorganic compounds of various metals and water-soluble organic resinous solids.

The rst oil phase from the extraction step may or may not contain relatively small amounts of solid or semisolid material. -Cooling the oil phase results in increasing the amount of this solid or semi-solid material. It has been found that for the purposes of this invention, the amount of this solid or semi-solid oil-soluble reject separated in the rejection step, plus the amount of Watersoluble reject from the rst solvent recovery stage should not exceed about 6%, and the amount of oil-soluble reject lshould not exceed about 5% by weight of the residual shale oil charged to the extraction system. The temperature and amount of solvent used in tthe rejection step are adjusted to accomplish this purpose. In single batch extraction, using a ratio of about l volume of acetone to 1 volume of oil gives the greatest amount of reject. Temperatures of the rejection step are preferably lower than the temperature in the extraction step, 'although room temperatures have been used in both stages successfully. Generally, the temperatures in the rejection step will be between about 60 F. and 160 F. The separation of the solid or the semi-solid material in the rejection stage may be accomplished by settling `and decanting, ltering, centrifuging or .other conventional processes; and the solvent recovery may be made by distillation, steam stripping, or similar conventional processes. It may be desirable to heat the feed oil somewhat when rst mixing with solvent, and then let it cool to the desired temperature of treatment.

In the processes of FIGURE 2 `and FIGURE 3 the conditions of the extraction stage are similar to those of FIGURE l except for the absence of the acetone in the extraction step of FIGURE 2. The amounts of water in the extraction stage of FIGURE 2 and FIGURE 3 may thus be between about 0.05 volume and l volume per volume of oil. 'Ihe amount of acetone used in the rejection stage of both FIGURE 2 and FIGURE 3 may lie between about 1 volume and 5 volumes per volume of oil.

The alcohol indicated in FIGURE 2 as used in the extraction stage may be methyl, ethyl or isopropyl alcohol or other relatively water-soluble alcohol containing not over about l0 carbon atoms and may be used in amounts eiective as anti-emulsification agents, up to about 10% of the -water used in the extraction.

The alcohol used in the rejection stage may also be isopropyl alcohol or other alcohols such as those used in the extraction stage. As indicated above, benzene or other aromatic hydrocarbons having fewer than about 10 carbon atoms may be used in the rejection stage in place of alcohol and in the same amounts. It is apparent of course that the alcohol shown in FIGURE 2 may also be employed in the processes of FIGURE l vand FIGURE 3; and the separate recovery of individual solvent as illustrated in FIGURE 2 may be also carried out in FIGURE 1 and FIGURE 3. It has also been found that other ketones which are homologs of acetone and contain not more than 6 carbon atoms, may be substituted in whole or in part for the acetone. When this is done, the temperature used in the rejection step should be lower than with acetone. Thus temperatures above about 50 F. are

generally used, but ambient temperatures may also be used as indicated above.

It has been found that Ithe above processes of -this invention have two other interesting advantages. By carrying out the processes as indicated above, not only is the oil made non-corrosive and suitable for hydrogenation, but its pourpoint is generally reduced from values in the neighborhood of 80 F. or higher to values of 40-50 F. In addition, the toil soluble reject material is a waxy material which may have a melting point in the neighborhood of 140 F.

`It has also been observed that the corrosivity of the residual shale oils is related to their chlorine contents; and that when the conditions of the water extraction step are adjusted so as to reduce the chlorine content to about 0.005% or lower, the products are substantially noncorrosive.

The following specific examples are illustrative of the invention.

Example I Crude shale oil produced by the downfiow process of the Berg Patent No. 2,501,153 was mixed with 3 Volumes of acetone and agitated while being heated to 135 F. over a period of about 0.5 hour. The mixture was then permitted to settle and cool for about 16 hours, at which time it had cooled to about 80 F. The mixture was filtered through No. 40 Whatman filter paper at this temperature, leaving about :4% of the original weight of the crude oil as a solid residue on the filter paper. The filtrate was vacuum distilled to remove the acetone, `and the remaining oil, which constituted about 96% by weight of the original crude, was tested in the filter bomb test described above in comparison with the crude oil feed. It was found that the original crude shale toil feed plugged the filter so quickly that substantially none of the oil could be filtered, whereas all of the acetone treated oil passed through the filter with no evidence of plugging and no perceptible precipitate. Photomicrographs of the feed and product were also taken, and whereas the feed showed evidences tof many solid or semi-solid particles of various sizes suspended in the oil, the product was substantially free of any particles.

When particles are referred to here it must be understood that these are not ordinary solid suspensions capable of removal by simple settling or filtration. These crude oils referred to herein have in many cases been stored for months and even maintained at temperatures of about 160 F. under a blanket of helium for months; and While there was in some cases a settling of `a ysmall amount of semi-solid material, the photomicro-graphs remained substantially the same, as did the plugging tendency in the bomb test and in actual pilot plant runs. Even filtration after such long standing had no Substantial effect on the appearance in the photomicrographs or on the plugging tendency. Yet the acetone treatment, which appears to remove primarily wax-like materials of relatively low melting point, not only clarified the oil but removed all tendency toward plugging or gunk formation during the subsequent hydrogenation. Since wax can be readily hydrogenated under the above conditions without causing any plugging of the hydrogenation reactor or preheater, the effect of the acetone treatment is quite surprising.

It is also interesting that when the crude shale oil feed is vacuum distilled to take 80% overhead, acetone treatment of the distillate as above resulted in rejection of -substantially the same amount of waxy solid material, and had almost exactly the same effect of reducing pourpoint, i.e., a reduction of about 40 F.; yet this distillate is free from plugging tendency in the filter bomb and hydrogenation tests, so that acetone treatment is of little benefit to the dlistillate in this respect.

The acetone-treated crude oil described above was found to be substantially as corrosive as the crude shale oil feed, i.e., both exhibited corrosion of carbon steel at 600 F. amounting to about 0.068 per year. One volume of the product was mixed with one volume of water at room temperature and the mixture was agitated while heating to 180 F. over a period of one hour and allowed to settle for one hour at which time it had cooled to about 150 F. The oil was decanted from the water and recovered to the extent of about 99.5% by weight. It was again tested for corrosivity and found to be substantially non-corrosive, i.e., its corrosion rate for carbon steel was only about 0.003 per year, which is well below the tolerable rate of about 0.008" per year. The waterwashed oil remained equally free from plugging tendency in the filter bomb test, and was suitable for catalytic hydrogenation without plugging of the preheater or catalyst bedv j Example Il When the above example was repeated using the process of FIGURE 3 with about one volume of acetone per volume of oil in the rejection stage, and adding about 0.1 volume of water per volume of oil (0.5 volume per volume of oil plus acetone) in the extraction stage, the water -being use in a three-stage counter-current extraction, substantially the same resultswere obtained except that about 5% of reject was obtained in the acetone treatment. The loss of `feed to the water amounted to about 0.5% in each case.

Example III Example IV When Example I was repeated using each of the modifications shown in FIGURES l, 2 and 3, substantially the same results were obtained. Thus in accordance with `FIGURE 1, the crude shale oil was first treated with 4 volumes of a mixture of acetone and water containing 25% by volume of water, at an initial temperature of about 150 F.; and the oil phase from this treatment was cooled to about F. and filtered. In this modification, the presence of the acetone had beneficial effects in reducing the mixing time since the acetone reduced the viscosity of the oil very materially. It also served to minimize emulsion formation. In the run made in accordance with FIGURE 2, about 10% of isopropyl alcohol was added to the water, and this served to minimize the emulsion difficulties and to reduce the viscosity of the oil slightly, although not as much so as with the acetone. About 10% of benzol was added to the acetone in the rejection stage, and this decreased the amount of reject to about 3% rather than 4%. In the run made in accordance with FIGURE 3, again the acetone had the beneficial effects mentioned above. In all three cases products of excellent quality as regards lack of corrosivity and resistance to plugging of the hydrogenation equipment were obtained.

Example V Example II was duplicated using methyl ethyl ketone (MBK) in place of the acetone; and again repeated using methyl isopropyl ketone (MIBK) in place of the acetone. With the MEK, the final temperature of the rejection stage was 65 F., and with the MIBK, the mixture was cooled to 50 F. before filtration. Ihe amount of reject obtained at these temperatures was about the same as the amount obtained with the acetone at the higher temperature, but there was more difficulty in filtration.

The products however were not corrosive and were free from plugging tendency.

Other modifications of the invention which would be apparent to one skilled in the art are intended to be included within the scope ofthe invention as defined in the following claims.

I claim.

1. A method of refining residual shale oil which comprises treating said oil with acetone and water so as to reject a total of about 2 to 6 Weight percent, based on the crude shale oil, of solid material, and subjecting the treated oil to an elevated temperature in contact with hydrogen at an elevated pressure.

2. In a method of rening residual shale oil which comprises contacting said oil with hydrogen at elevated temperatures and pressures, the improvement which comprises pre-treating said oil with acetone and water in the liquid phase so as to separate therefrom a Water-soluble reject and a solid material which together constitute a totalof 2 to 6 weight percent, based on the crude shale oil, of reject, and separating a product comprising at least about 94% of the residual shale oil, which product is substantially non-corrosive and has an improved resist ance to precipitation in the presence of hydrogen at elevated pressures.

3. A method of reining residual shale oil which comprises treating said oil withacetone and water at temperatures between about 60 F. and 200 F. so as to form a total of 2 to 6 weight percent, based on the crude shale oil, of solid material and obtain a solution of acetone and treated shale oil, and separating said solid material, acetone and water from the treated shale oil.

4. A method according to claim 3 in which an alcohol having not more than about 10 carbon atoms is used in an amount not exceeding about 10% of the water.

5. A method according to claim 3 in which the residual shale oil is iirst treated with at least about 0.5 volume of water at a temperature above about 100 F. to separate water-soluble materials therefrom, and the watertreated oil is treated with about 0.5 to 5.0 yvolumes of acetone at a temperature not lower than about 60 F.

6. A method as dened in claim 5 wherein said oil is treated with water at a temperature from, about 150 F. to 180 F.

7. A method according to claim 6 in which an alcohol having not more than about 10 carbon atoms is used in an amount not exceeding about 10% of the water.

8. A method according to claim 6 wherein an aromatic hydrocarbon having not more than 10 carbon atoms is used with the acetone in an amount not to exceed 10% of the acetone.

9. A method according to claim 3 in which the residual shale `oil is rst treated with about 0.5 to 5.0 volumes of acetone to reject solid material, and the acetone-treated oil is Washed with at least 0.5 volume of Water.

10. A method according to claim 9 in which at least part yof the acetone is removed prior to Water extraction.

11. A method of refining residual shale oil which comprises treating one volume of said oil with a total of about 2 to 6 volumes of a mixture of water and acetone containing at least 0.05 volume of water, said mixture also containing between about 50% and 98% by volume of acetone, at a temperature between about 60 F. and 200 F. to `form` an oil phase and an aqueous phase; the oil phase is separated and subjected to a temperature between about 60 F. and 100 F. to reject solid material; the solid material is separated; and the acetone solvent is separated from the solid-free oil.

l2. A method of refining residual shale oil which comprises treating said oil with acetone at a temperature between about 50 F. and 200 F. so as to reject 2 toy 6 weight percent, based on the crude shale oil, of solid material and recover an oil having an improved resistance to precipitation in the presence `of hydrogen at elevated pressures.

13. A method according to claim 9 in which a homolog of acetone having not more than 6 carbon atoms is substituted Vfor at least part of the acetone, and a lower temperature, not less than 50 F., is employed in the treatment.

References Cited in the file of this patent UNITED STATES PATENTS 1,760,129 Fischer et al. May 27, 1930 2,137,499 Moravec Nov. 22, 1948 2,606,141 Meyer Aug. 5, 1952 2,692,226 Smith Oct. 19, 1954 2,825,678 Iahnig et al. Mar. 4, 1958 2,943,047 Reeg et al .Tune 28, 1960 

1. A METHOD OF REFINING RESIDUAL SHALE OIL WHICH COMPRISES TREATING SAID OIL WITH ACETONE AND WATER SO AS TO REJECT A TOTAL OF ABOUT 2 TO 6 WEIGHT PERCENT, BASED ON THE CRUDE SHALE OIL, OF SOLID MATERIAL AND SUBJECTING THE TREATED OIL TO AN ELEVATED TEMPERATURE IN CONTACT WITH HYDROGEN AT AN ELEVATED PRESSURE. 